Dear Liz: After reading your column about the best ways to pay while traveling in Europe, I want to share my experience. I was unhappy with the foreign transaction fee charged on my Citibank credit card, so on my next trip to Europe I primarily used my Capital One card. Imagine my disappointment to find that Capital One’s currency conversion formula was much less favorable to me than Citibank’s.

Answer: Credit card expert Odysseas Papadimitriou suspects you were comparing purchases made on different days, or even on different trips. Although one of your cards charges a foreign transaction fee and the other doesn’t, both cards get the most favorable rate from their card network’s exchange rate. Visa cards would get the Visa card network exchange rate, while MasterCard would get the MasterCard network exchange rate. If both your cards were Visas, for example, they would get the same exchange rate, but the one that charged the foreign transaction fee would increase your cost by that amount (typically 1% to 3%).

There may be “tiny” differences between those Visa and MasterCard exchange rates on a given day, but one wouldn’t be “much less favorable” than the other, Papadimitriou said.

And the exchange rates are certainly better than what you’d get by exchanging dollars for euros at a bank in advance of your trip, or by using currency exchange services once you got there.

So the fact remains that the cheapest way to convert currency is to do so automatically by making purchases with a credit or debit card that doesn’t charge foreign transaction fees. Here’s another suggestion for reducing fees abroad:

Dear Liz: One option for folks traveling to Europe to save money on ATM withdrawals is to check with their bank and find out if there is a checking or savings account that carries the benefit of the bank canceling foreign ATM fees as well as their own fees. Before I traveled to Scotland to visit my daughter, I switched accounts at my bank to one where there are no fees for using other banks’ ATMs. Worked brilliantly!

Answer: If your own bank doesn’t offer this option, it may be worth setting up a checking account with a bank that does. As mentioned in the previous column, Charles Schwab’s high-yield checking account offers unlimited ATM fee rebates worldwide with no foreign transaction fees, and Capital One 360, the online bank, waives ATM fees and absorbs MasterCard’s 1% foreign transaction fee. USAA Bank charges a 1% foreign transaction fee but doesn’t charge a fee for the first 10 ATM withdrawals.